Can company A make amendments to change to concurrent and part time while I have a new H1 with company B?

[need_assistance]

Recently I have moved from company A (full time) to company B (full time) on H1 visa.

Now, I want to work for company A on part time.

My questions are:

1. Can company A file amendment to convert company A's H1 to concurrent and also from full time to part time?

2. Since company B will not be aware that Iam working for company A on part time, will there be any situation where I will have to reveal this information to company B?

Now, company B is going to initiate Green card for me and I want to make sure that, I will not have any issues and also not require to provide company A's visa information.

Thanks.